Internal combustion engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of gaseous compounds, which may include nitrous oxides (NOx), and solid particulate matter, which may include unburned carbon particulates called soot.
Due to increased attention on the environment, exhaust emission standards have become more stringent, and the amount of gaseous compounds emitted to the atmosphere from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine. One method that has been implemented by engine manufacturers to comply with the regulation of these engine emissions is exhaust gas recirculation (EGR). EGR systems recirculate the exhaust gas byproducts into the intake air supply of the internal combustion engine. The exhaust gas directed to the engine cylinder reduces the concentration of oxygen within the cylinder and increases the specific heat of the air/fuel mixture, thereby lowering the maximum combustion temperature within the cylinder. The lowered maximum combustion temperature and reduced oxygen concentration can slow the chemical reaction of the combustion process and decrease the formation of NOx.
In many EGR applications, the exhaust gas is passed through a particulate filter and catalyst containing precious metals. The particulate filter may capture a portion of the solid particulate matter carried by the exhaust. After a period of use, the particulate filter may become saturated and may require cleaning through a regeneration process wherein the particulate matter is purged from the filter. In addition, the catalyst may oxidize a portion of the unburned carbon particulates contained within the exhaust gas and may convert sulfur present in the exhaust to sulfate (SO3).
The regeneration process may include using a regeneration device coupled within an exhaust treatment system. In some examples, the regeneration device may include an ignition system having, for example, a fuel injector and an electrical energy delivery device to facilitate combustion within the regeneration device. U.S. Pat. No. 5,189,333 issued to Kagawa et al. discloses an electrical energy delivery device which may be used with a fuel injector to ignite an air-fuel mixture such as via an electric spark. The electrical energy delivery device, or spark plug, of Kagawa et al. includes a central electrode and a parallel ground electrode. The central electrode protrudes from a lower end of an insulator. The insulator may be coupled to a main metal shell of the electrical energy delivery device. The parallel ground electrode is arranged opposite to the central electrode. One end of the ground electrode may be bonded to a main metal shell. An air-fuel mixture may be ignited by a spark discharge in an air gap between the central electrode and the parallel ground electrode.
However, the ignition system of Kagawa et al. may provide inconsistent ignition of the air-fuel mixture during one or more ignition attempts. For example, the amount and/or concentration of the air-fuel mixture may fluctuate around the ignition area, or air gap, in the design of Kagawa et al. Hence, a poorly positioned ground electrode, for example, one being positioned relative to the central electrode for generating an appropriate electrical current in an air gap therebetween, may not be able to provide proper ignition. The arrangement provided by Kagawa et al. may also allow fouling, such as carbon deposit build-up, to develop along components of the electrical energy delivery device. These components may include surface portions along the central and ground electrodes. Such fouling may also prevent proper ignition of the air-fuel mixture. Furthermore, the placement of the ground electrode with respect to additional components of the electrical energy delivery device of Kagawa et al., including, for example, the central electrode, may allow arcing outside of the air gap in the ignition area. This may include arcing along portions of the central or ground electrode connected to the base portion of the electrical energy delivery device. Arcing outside of the gap ignition area may also yield unfavorable and inconsistent ignition results.
The present disclosure is directed towards overcoming one or more shortcomings set forth above.